Question

Why is symmetric encryption also called private key cryptography?

Describe the steps for a user named Mike to send a digitally signed message to a user named Sophie.

List the four characteristics a hash algorithm should have if it is to be considered secure.

Answer 1

Symmetric Encryption :

In the process of sending a message from the sender to the receiver, first, the plain text is converted to the ciphertext using an encryption algorithm and then the ciphertext is converted back to the original plain text using the decryption algorithm. If the same key is used in the encryption and decryption algorithm then it is known as the symmetric encryption which is also called private key cryptography.

Steps:

Step 1. Mike will have the plain text which he wishes to send

Step 2. He will use an encryption algorithm with a secret key by which he will convert the plain text to the ciphertext.

Step 3. Now the encrypted message will pass through a communication channel.

Step 4. The message is received at the receiver end by Sophie.

Step 5. Sophie will use a decryption algorithm with a secret key by which she will convert the ciphertext to plain text.

Characteristics that a hash algorithm should have  :

1. The output of the hash algorithm must be of a finite and fixed length.
2. For two different messages, there should not be the same hash value.
3. For a certain or a given message, there should be easiness in finding the hash function.
4. To increase the security of a hash algorithm, it must use the features of SHA ( Secure Hash Algorithms ).
5. The hash function must use all input data.
6. The hash function should uniformly distribute the data across the entire set of possible hash value